Counting system



July 13, 1937. A. J. M MASTER COUNTING SYSTEM Filed Aug. 20, 1932 2 Sheets-Sheet l I rule/1E7" "Bu M v 7778?? i Patented July 13, 1937 PATENT OFFICE COUNTING SYSTEM Archie J. McMaster, Highland Park, 111., assignor to G-M Laboratories, Inc., Chicago, 111., a corporation of Illinois Application August 20,

2 Claims.

. My invention relates generally to counting sys tems and more particularly to production counting systems for controlling subordinate machine operations. 5 In the process of filling packages or containers from conveyors or other automatically operated machines of various kinds, it is often desirable to count the product as it is delivered to the package. It is further desirable to count out the product into packages or lots containing a predetermined number of articles.

Various devices, including light sensitive cell systems, have been employed for this purpose, but such prior devices have been seriously limited in their speed and accuracy of count, in their promptness of response in actuating subordinately controlled equipment, and in the type of articles that could be handled.

In electric counting systems employing light sensitive cells difficulties more or less peculiar to this type of systems are encountered. This is especially so in a system used with a photoelectric cell wherein a. long lead extends from the cell to the control grid of an amplifier, as, for example, when the cell and amplifier are separately housed and located at a considerable distance from each other, which is usually neces sary.

It is accordingly an object of my present invention to provide an improved means for accurately counting the number of objects passing a given point in rapid succession.

A further object is to provide means for accurately recording the count of such objects. 35 A further object is to provide in a counting device means for automatically grouping the counted articles into lots of any selected predetermined numbers of articles.

Another object is the provision of improved photoelectric means for actuating a counting device or similar apparatus.

A still further object is to provide an improved method of shielding grid connections in electronic amplifiers employed in counting systems.

Other objects and advantages will appear as the description proceeds.

In order to acquaint those skilled in the art with the teachings and practice of my present invention, I shall now describe some specific embodiments thereof, reference being had to the accompanying drawings forming a part of this specification, and in which:

Figure 1 illustrates, partly in diagram, one form of the preferred embodiment of my invention; 5 and 1932, Serial No. 629,722

Figure 2 illustrates similarly another embodiment of the principles of my present invention.

In general the counting system shown and described herein employs a photoelectric cell, normally illuminated by a beam of light which is arranged to be interrupted so as to darken the cell by each of the objects to be counted as they pass along a conveyor or the like. The photoelectric cell in being thus alternately darkened and illuminated exhibits an impulse-like response which is suitably amplified and caused to actuate a group of indexing counting switches. The counting switches are arranged in successive stages to count the impulses in units, tens and hundreds, and are each provided with indexing or counting contacts which assume a different contact combination for each number within the capacity of the system. A number of selector switches are associated with the indexing contact combina-= tion for completing a circuit, so that the switches as they count the passage of the objects thru the light beam assume the several contact combinations in turn until reaching the selected combination whereupon the switches reset to zero to repeat the count. In resetting they effect the actuation of a subordinate apparatus which preferably consists of an automatic device for physically separating the counted objects into groups, as, for example, by controlling the operation of the conveyor carrying them or by directing them into an empty container. 0n the other hand, the subordinate apparatus may merely actuate a signal for directing a manual sorting of the objects into groups.

Thus, for example, if it were desired to pack the counted articles into packages of one gross each, the selector switches would be set for the number 144. The counting switches would then count to 144 and repeat and control the packaging equipment accordingly. Should it then be desired to place a difierent number of articles in each package it is merely necessary to readjust the selector switches to the new number.

In Figure l, I have illustrated a number of articles or objects 2 i which are to be counted as they pass along on a conveyor 22. A suitable light source 23, including a lens system when necessary, directs a beam of light across the path of the objects 2! to a photoelectric cell or light sensitive device 24, the beam of light being so directed that it is substantially interrupted upon the passage through it of each of the objects 21. The photoelectric cell comprises a cathode 26 and an anode 2'1 which are connected by means of relatively long leads or conductors 28 and 2B, respectively, into the circuit of an associated amplifier, the amplifier being located at a considerable distance from the photo-cell 24.

The amplifier is powered by a suitable transformer 32, including a primary winding connected to an alternating current supply. The amplifier further includes an electron valve 33, having a cathode 34, a control grid 35,'and a plate 36. A secondary winding 39 of the transformer 32 imposes an alternating voltage between the cathode 34 and the plate 36, an electromagnet winding 31 of a relay 38 being connected in series therewith. Another secondary transformer winding 48, together with a potentiometer 4| connected across its terminals, provides an adjustable alternating voltage for biasing the grid 35 relative to the cathode 34. A second potentiometer 42 is connected across the transformer winding 39 to provide an adjustable control voltage, which is applied to the anode 21 of the photoelectric cell 24.

The bias voltage is applied to the grid 35 through a capacity coupling comprising a condenser 45. The bias potential is also applied to a shield 46 surrounding the conductors 28 and 29. The shield 46 and the conductors 28 and 29 exhibit certain mutual capacities which are represented by capacities 41, 48, and 49 indicated in dotted lines, the capacity 41 between the sheath 46 and the grid connection 28 shunting the condenser 45. It will usually be found that there is a certain optimum capacity for the coupling of the grid to its bias voltage, and it will, there'- fore, be desirable to select the condenser 45 so that the sum of the capacities 45 and 41 equal that optimum value. Accordingly, the condenser 45 may under certain conditions be eliminated entirely.

The relay 38 is provided with an armature 5| which is arranged to operate normally open contacts 54 and normally closed contacts 55 and 56. These contacts are connected by means of conductors 51, 58, 59 and 68 with a counting device to actuate the same.

The counting device comprises a series of stepping switches or indexing means 6|, 62 and 63 and certain other apparatus associated therewith. The switch 6I comprises a rotatable armature or movable member 61 which carries a contact finger 68 and a ratchet 69; The armature is movable through a predetermined are or path of motion to bring the contact finger 68 into successive engagement with a plurality of contacts 18. A magnetically operable pawl 12 is engageable with the ratchet 69 to step the finger 68 from one contact 18 to the next from left to right, while a magnetically releasable detent 13 engages the ratchet 69 to hold it against the force of a spring 14 in any stepped position which it may occupy. The pawl is held normally clear of the ratchet 69 by means of a spring so as to avoid interfering with the return of the ratchet to its initial position upon its release by the detent 13.

The indexing switch 6| is also provided with a pair of interlocking switches 11 and 18. The switch 11 is spring closed and engageable by the armature 61 to be opened thereby when the latter moves to its extreme left position, while the switch 18 is normally open and is arranged to be closed by the armature 61 when the latter moves to its extreme right position.

These switches 11 and 18 are arranged to control the operation of an auxiliary relay 88, which in turn has contacts 8|, 82, 83 and 84 for controlling'the pawl 12 and the detent 13 and also the indexing switches 62 and 63 in response to the operation of the switch 6I.

Associated with the contacts 18 is a selector switch 86, having a movable contact arm 81 adapted to engage singly each of a series 01' contacts 88, one of which is connected to each of the contacts 18.

The indexing switches 62 and 63 together with certain of their auxiliary apparatus are similar to the switch 6| and its apparatus. I have accordingly indicated corresponding parts of the indcxing switches etc. by similar reference characters, a suffix (a) being added to the characters applied to switch 62, and a sufllx (b) to those applied to the switch 63, thus 18a etc. The indexing switch 63 differs from switches 6| and 62 in that it has no interlock switch corresponding to the switches 18 and 18a. Associated with the switches 62 and 63 are auxiliary relays 89 and 98, respectively corresponding to the relay 88. The relay 89 is provided with contacts corresponding to those of the relay 88 and also with a contact 85 for connecting the interlock switch 11a in shunt with the switch 11. The relay 98 is provided with a greater number of contacts than the relay 88 so as to adapt it under certain conditions to control the operation of relays 88 and 89. These contacts are indicated by the reference numeral 94.

The relay 98 is also arranged to actuate a pilot relay 9| in response to the operation of the indexing switches 6|, 62 and 63 to effect a control of a connected apparatus 92, which may be arranged to perform any desired operation such as controlling the conveyor 22, suitable packaging equipment or the like. A manual reset switch 95, having sequence operated contacts 96 and 91 is also provided.

Power is supplied to the various circuits of the counter from a pair of power buses I88 and I 8| The actuating circuit for the indexing switches 6|, 62 and 63 may be traced from the bus I8I through the conductor 68, contact 56 of relay 38, conductor 51 to the contacts 82 and 83 of relay 88. Under certain conditions, the circuit will pass thence along a conductor |82a to the contacts of the relay 89, thence to the contacts of relay 98 and to the coil of relay 9| from which the circuit returns to the opposite power bus I88. These several relays 88, 89 and 98 control the continuity of various parts of this circuit and operate at certain times to extend the same to the various pawl and detent magnets 12, 13, etc.

An interlocking bus I85 is connected to the power bus I8| through the normally open contact 54 of the relay 38. A counting control, or selector circuit extends from this interlocking bus along a conductor I86 to the selector switch 86, thence through the indexing contacts 18 and the contactor 61 of the switch 6| to a conductor I 86a and similarly through the other selector and indexing switches to the contactor arm 61b of the indexing switch 63 thence along a conductor I81 through the coil of the relay 98 to the power bus I 88.

In operation the photoelectric cell 24 is Hormally illuminated by the beam from the light 23 and is at least partially darkened upon each passage of one of the objects 2| before it. The cell responds to this decrease of illumination by, exhibiting a corresponding decrease in its conductivity, which decrease in conductivity acts to control the operation of the amplifier. In the amplifier, under any particular set of conditions, certain currents will flow in the grid and plate circuits of the tube 23, the magnitude of which currents will depend in part upon the amount of light entering the photoelectric cell 24, and the settings oi the potentiometers 4| and 42.

The valve 23 and the cell 24 exhibit a rectifying action when operated on alternating current and consequently, current flows in the plate circuit of the valve 33 during only one half of each volt- 'age cycle, that half cycle being the one which imposes a positive potential on the plate 26 relative to the cathode 24. When the plate 28 is positive, the grid bias potential is negative relative to the cathode.

It will be noted that the grid of the valve 33 is in eflect positioned in a series circuit extending between the variable voltage taps of the two potentiometers 4| and 42, beingconnected through the photoelectric cell 24 to the potentiometer 42 and through the condenser 45 and the capacity 41 to the potentiometer 4|. Consequently, the grid potential is determined essentially by the relative impedances of the cell 24 and the combination of the condenser 45 and the capacity 41. When the conductivity of the cell 24 decreases, due to its being darkened by one of the objects 2|, that is when its impedance increases, the relation of its impedance to that of the condenser 45 taken together with the capacity 41 is so altered as to impose a greater bias voltage on the grid. In other words, assuming the bias voltage to be negative, the grid potential is lowered by the darkening of the cell 24.

It will also be noted that the circuit controlling the grid potential is one of very high impedance, the cell 24 having an impedance oi the order of several megohms. Because of this, the grid potential is susceptible under certain conditions to being controlled by external influences in a degree comparable to the control exercised by the operation of the cell 24 itself. However, the shield 46 which encloses the grid connection 28, since it is connected to the potentiometer 4|, is maintained at a predetermined voltage so as to effectively prevent such external influences from affecting the grid of the amplifier.

I have found that a circuit such as I have herein described is substantially unailected by external disturbances and provides a more sensitive response to the operation of the photocell than do any circuits heretofore employed to meet similar conditions.

The objects 2| in interrupting the light beam, therefore, lower the potential of the grid 35 (assuming the plate potential to be positive) to cause a decrease in the current flowing in the plate circuit, and in emerging from the beam permit the plate current to again increase to its full value. This pulsing plate current traverses the winding 31 of the relay 38 and if the current is of the proper value and the variation suilicient, it will cause the relay first to drop and then pick up its armature 5| as an object passes through the light beam. The plate current may be adjusted so as to produce this operation of the relay by increasing the control voltage by means of the potentiometer 42 until the armature picks up with the photoelectric cell 24 illuminated, and by increasing the grid bias voltage, that is, lowering the bias potential when the plate is positive, by means of the potentiometer 4| until the re lay 38 drops its armature with the cell 24 darkened due to the passage of one of the objects 2| through the light beam.

Since these two adjustments are inter-dependent, it may be necessary after adjusting the bias voltage to further increase the photo-cell control voltage. In such case the adjustment of the potentiometer 42 should be carried somewhat beyond the point at which the armature of relay 38 picks up when the cell 24 is illuminated. The grid bias voltage should then be re-adjusted to cause the relay 2. to drop out when the cell is darkened by one of the objects 2|.

When the relay 2. releases its armature as a result of an object 2| interrupting the light beam, it operates its three contacts in the following sequence: It first closes contact 55; it then opens contact 54 to isolate the interlocking bus I05; and it finally closes its contact 56 to transmit an electric impulse to the indexing or countingv switches. When the armature picks up the operation it is in the reverse order, namely: contact 56 opens, contact 54 closes and contact 55 opens.

Assuming that the relay 80 is de-energized, its normally closed contact 82 will transmit the impulses to the magnet operating the pawl 12 to index the contactor arm 61 toward the right so that it steps from one contact to the next each time an object 2| enters the light beam. If the contactor 61 starts from its extreme left position in engagement with the first contact, it will, after eight impulses, be in engagement with the ninth contact. Upon being indexed by the ninth impulse into the extreme right position, (where it engages the tenth one of contacts 10) it engages the switch 18 by means of an insulating bumper to close the same. The switch 18 thereupon establishes a circuit from the interlocking bus I05, through the contact 84 to the coil of the relay 80. During the interval following the ninth impulse, that is after the ninth object leaves the light beam, the interlocking bus I05 becomes energized through contact 54 of relay 38 and causes the relay 80 to operate, closing the contact 8| and thereafter opening the contact 84. This leaves the coil of relay 80 energized from power bus through the interlock switch H and the relay contact 8!, which constitute a holding circuit. The relay 80 will now maintain itself until the switch 11 is opened. The contact 84, in opening, has disconnected the coil of relay 8!) from the interlocking bus I05 so as to avoid energizing the same through the relays holding circuit. The relay 80 in operating has also opened the contact 82 and closed the contact 83 so as to condition the circuit to transmit the next impulse to the magnet of the detent l3 and to the contacts of relay 89, which if we assume that the relay 89 is deenergized, will direct the impulse to the magnet of the pawl 12a. Assuming then that the contactor arm 61a of relay 62 is lying in its extreme left position, that is in engagement with its first contact, the next or tenth impulse, which occurs as the tenth object enters the light beam, will operate the pawl 12a to index the arm 61a. to its second position and will at the same time operate the detent 13 to permit the arm 61 to return under the action of the spring 14 to its extreme left or original position, where it engages the switch TI to open the same. It should be noted that as long as the armature of relay 38 is released due to the object remaining in the light beam, the contact 55 shunts the interlock switch 11 to maintain the holding circuit of the relay 80. This positively prevents the relay 80 from re-closing the circuit to the magnet of the pawl 12 until after the tenth impulse.

That is, it prevents the relay 66 from operating to energize first the detent I6 and then the pawl 12 inv response to one and the same impulse. Therefore, after the tenth impulse, that is after the tenth object leaves the light beam, the contact 66 opens so that the relay 66 returns to its normal position with its contacts II and 63 open and its contacts 62 and 64 closed, so as to condition the circuit to transmit the subsequent impulses to the magnet of the pawl 72 to again step the arm 61 through its path of travel. It is thus seen that the arm 61 is repeatedly indexed toward the right by nine impulses and then returned to its starting position by the tenth, each tenth impulse being also transmitted to pawl 12a to operate indexing switch 62. The indexing switch 62 operates in the same manner as does the switch 6 I, being indexed toward the right by nine impulses and returned to its starting position by the tenth, each tenth impulse received by the switch 62 being also transmitted to switch 63. The tenth impulse received by the switch 62 will of course be the hundredth impulse and the tenth received by the switch 63, the thousandth.

When the relay 66 is energized in response to the indexing arm 61a reaching its extreme right position, it closes a holding circuit through its contacts 65 to the contacts 65 of the relay 36.

The purpose of the holding circiut is to prevent the relay 66 from releasing before the end of the impulse which operates the detent 13a in the same manner as described in connection with the relay 66.

It will be noted that the ten selector contacts 66 of switch 66 which are connected to indexing contacts 16 of indexing switch 6| are numbered 1 to 10 inclusive and that the selector contacts of each of the other switches are numbered from 0 to 6 inclusive. Thus, the indexing switch 6| is always connected to a selector contact corresponding to a number one unit greater than the number of impulses that it has received. This means that the first impulse steps the arm 61 into engagement with the second indexing contact which is connected to selector contact number 2, the second impulse completes the circuit to contact number 3, etc. On the other hand, the arm of each of the indexing switches 62 and 63 always makes a circuit to a selector contact cor.- responding to the number of impulses which it has received. For example, as shown in the drawings, the indexing switch 63 indicates the number 2, switch 62 the number 4 and switch 6| the number 4; that is, the three indexing switches indicate the number 244 which is the condition obtaining after receiving 243 impulses.

The selector switches 66, 86a and 66b are set for the number 654. After 653 impulses each indexing arm will be connected through the indexing and selector contacts to the arm of its corresponding selector switch. A circuit will accordingly be completed from the interlocking bus I65 along conductor I66 through all the selector and indexingswitches, along the conductor I61 to the coil of relay 66 and thence to the power bus I66. During the interval between the 653rd and 654th impulses, the normally open contact 54 of the relay 36 (when the relay 36 picks up) will connect the interlocking bus I65 to the power bus |6| so as to energize the relay 66, causing it to close its contact 63 to establish a holding circuit direct from the bus |6| through the interlocking switch "b. It will also close the contacts 64, one of which is connected to each of the relays 66 and 66 to energize the same which also estab- 6| are connected together.

llsh holding circuits through the switches I1 and 11a and the contact 66 of the relay 36. The bolding circuitswill be then all connected in parallel so that all must open before any of the relays 66, 66 or 66 will release. The impulse circuit will, at the same time, be connected to the magnets oi all the detents 13, 13a. and 13b and to the coil of pilot relay 6|.

Therefore, upon the occurrence of the 664th impulse, that is when the 854th object enters the light beam, the relay 6| operates to actuate the subordinate apparatus 62, and the several indexing arms return to their starting positions,

thereby opening the switches 11, Ila and Ilb to release the relays 66, 66 and 66. The apparatus is tlsien ready to begin counting out another group of 54.

It thus will be seen that the indexing switches 6|, 62 and 63 each function as a counting device or counting means. The indexing switch 62 serves to repeatedly count out groups of 10 of the impulses transmitted by the operation of relay 36. The indexing switch 62 serves to count the number of impulses which are transmitted to it through the contact 63 of the relay 66. In so doing it counts the number of times that the contactor 61 of the indexing switch 6| is reset to its starting position; that is, it counts the cycles of operation of the indexing switch 6|. Similarly, the indexing switch 63 serves to count the number of cycles of operation of the indexing switch 62.

It also will be seen that the relays 66, 66 and 66 function to control the reset operations of the indexing switches 6|, 62 and 66 respectively. Therefore these relays constitute reset control means. The actual resetting of the contactors of the indexing switches is accomplished by the magnets of the detents 13, 13a and 13b together with the springs, such as the spring 14, which serve to bias the contactors 61, 61a and 61b to their starting positions. Thus the magnet associated with the detents 13 of the indexing switch 6| together with the return spring 14 constitute means for resetting or returning the contactor 61 to its extremeleft or starting position.

In the operation of any counting system it obviously is important that no counts be recorded due to extraneous influences. When operated continuously my improved counting system will make an accurate count and will properly control a grouping or packaging device in accordance with any number that may be selected.

When first putting the device into operation .it will usually be necessary to experiment somewhat by passing several objects through the light beam in order to adjust the potentiometers 4| and 42 in the manner already described to obtain a proper operation of the relay 36. It will be apparent that the specific adjustment required I of the potentiometers 4| and 42 will depend upon the size and opacity of the objects to be counted. When this adjustment has been made the light beam should be left unobstructed so that the relay 36 draws up its armature. The manuat reset switch 65 should then be operated to set the indexing or counting switches to their zero positions. The switch 66 first closes its contact 66 to energize the relay 66 which when it-operates, energizes the relays 66 and 66 through its contacts 64 so that the magnets of the several detents 13, 13a and 13b and the coil of relay The switch 65 then closes its contact 61 to energize the detents 13, 13a and 13b and the relay 6|, thereby bringing all the indexing arms 61, 61a and 61b to their starting positions and actuating the subordinate apparatus 92 for separating the few articles used in the preliminary test from those to be subsequently counted. The selector switches may be set according to the numbers appearing on the selector contacts for any quantity from one to a thousand inclusive. I

Should it be desirable to discontinue operation, as, for example, when shutting down over night, or the like, the conveyor 22 should be stopped in such position that the objects 2| do not interrupt the light beam, power should then be removed from the buses I and IM of the indexing switches and then the transformer 32 may be de-energized. To restart the transformer should bev reconnected to its power supply, and then after waiting for the light source 23 and the cathode 34 of the valve 33 to come up to proper temperature so that the relay 38 draws up its armature, power may be applied to the buses I00 and WI and the operation of the conveyor resumed.

In Figure ,2, I have illustrated a slightly modifled system for carrying out my present invention. It includes a photoelectric cell and amplifier circuit which differs from that shown in Figure 1, in the manner of shielding the leads which extend between the cell and its amplifier.

A photoelectric cell or light responsive means III has its cathode I I2 connected by means of a conductor H3 to the grid H4 of an electron valve H5. A bias voltage is applied to the grid H4 through a condenser H8 and to a sheath I20 surrounding the conductor H3 by means of a connection I2I. A lead I23 from the anode I24 of .the cell III lies outside the shield I20, though in practice it may be in close proximity thereto, being assembled into the same cable therewith. The shield I20 exhibits a certain capacity with respect to each of the conductors H3 and I23. These are indicated as capacities I21 and I28 shown in dotted lines. A ground connection may be applied to the circuit at any suitable point, as, for example, at connection I29 so as to apply ground potential to the oathode I30 of the electron valve, or at connection I2I so as to ground the shield I20.

The deviceof Figure 2 also includes a counting means comprising a bank of indexing switches I33, I33a and I33b, having selector switches I34, I34a and I34b associated therewith. The indexing switches are provided with magnetically operated detents I42, I420, and I421),

of which detents I42 and I420. have each two coils, and with interlock switches I43 and N301. Power for operating the counter is supplied from a pair of buses I44 and I45. The magnet of the pawl MI is arranged to be energized through an actuating circuit I46 by the contacts of relay H6 so as to index the switch I33 in response to the passage of objects through the light beam. The detent I42 of indexing switch I33 and the pawl I4Ia of switch I33a are under control of the interlocking switch I43 which is operable by the indexing switch I33 when indexed into its tenth or extreme right position. Similarly, the detent M211. and the pawl I4Ib are under the control of the interlocking switch I43a.

A pilot relay I4I for controlling a subordinate apparatus I48, together with the magnetic detents I42, MM and M21) are arranged to be actuated in response to either the operation of the indexing or counting switches in accordance with the setting of the selector switches, or the operation of a normally open manual reset switch I50.

In operation, the device oi Figure 2 counts objects .passing before the photoelectric cell in much the same manner as does the device of Figure 1.

However, under certain conditions the photocell and amplifier of Figure 2 is more sensitive in its response than is that of Figure 1, because of the relations existing between the mutual capacities of the cell leads H3 and I23 and the shield I20 in view of the optimum capacity for the coupling between the grid and the source of its bias. voltage. It is desirable to keep the capacity between the leads H3 and I23 low in comparison to the sum of the coupling capacities H8 and I2! in order to avoid having an excessive capacity shunt across the terminals of the photoelectric cell. In the circuit of Figure 2, this shunt capacity is minimized by carrying the conductor I23 outside of the shield I20. The arrangement of Figure 2, therefore provides a greater inherent sensitivity in the photoelectric cell and its amplifier so as to permit the use, under certain conditions, of much longer leads.

As in the device of Figure 1, impulses are transmitted to the counter in response to the passing of objects before the photoelectric cell. The impulses actuate the pawl IM to index the arm of the relay I33, which steps up one position in response to each impulse. The tenth impulse moves the arm of the relay into its extreme right or tenth position to actuate the interlock switch I43. Upon closing, the switch I43 energizes one winding of the magnet of the detent I42 and also the magnet of the pawl I4Ia so as to simultaneously index the relay I33a from its first or rest position into engagement with its second indexing contact, and release the arm of the relay I33 to permit its return to its rest position. It will be noted that the switch I43 maintains the coils of the pawl I4Ia and the detent I42 energized only so long as the'arm of relay I33 occupies its extreme right position. For this reason, it is desirable that the pawl be comparatively quick acting while the detent should be slower than either the pawl or the relay arm. The detent thereby holds the switch I43 closed until the pawl has time to operate, and then when it releases the relay to cause its own de-energization maintains disengagement long enough to permit the relay to return to its rest position.

Thus, after ten impulses the relay I33 occupies its rest position so as to provide a connection to the selector contact marked "0 while the relay I33a occupies its second position so as to engage the indexing contact marked "1. In a like manner, relay I33b is indexed one step at each hundredth impulse.

When the indexing relays have received the number of impulses indicated by the setting of their selector switches, they operate to return themselves to their zero or starting positions at the extreme left of their respective arcs of travel, and at the same time actuate the pilot relay I41 to control the associated apparatus I40. As shown in the drawings the selectors are set at the number 6'75 and accordingly upon the occurrence of the 675th impulse, the circuit is closed through the several indexing arms and the selector switches, to the relay I41 and to one of the coils on the magnet of each of the detents I42, I42a and M21). The relay I41 thereupon draws up its armature to close a circuit to the device I48 apparatus 8 is also actuated when the counting switches are reset manually.

While I have shown and described certain specific embodiments of my invention, it will be apparent to those skilled in the art that such embodiments are shown merely by way of example and that the principles thereof are capable of a much broader application. I, therefore, do not wish to be limited except by the scope of the appended claims.

I claim:-

1. In a system or the class described, means for producing electric impulses, an indexing switch having a reciprocable contactor biased to starting position and operable through steps, a first electromagnet for operating said contactor through said steps, one step at a time for each impulse, retaining means for retaining said con-.

tactor in advanced position, a second electromagnet for releasing said retaining means to permit said contactor to return to starting position in response to a single impulse, a relay adapted to direct impulses to either of said electromagnets and adapted fiirther to operate when said contactor reaches a predetermined stepped position so as to direct an impulse to said second electromagnet and operable further when said contactor has returned to its starting position to direct impulses to said first electromagnet.

2. In a system or the class described, means for producing electric impulses. an indexing switch having a reciprocable contactor biased to starting position and operable through steps, a

first electromagnet for operating said contactorthrough said steps, one step at a time for each impulse, retaining means for retaining said contactor in advanced position, a second electromagnet ior releasing said retaining means to permit said contactor to return to starting position in response to a single impulse, a relay adapted to direct impulses to either of said electromagnets and adapted further to operate when said contactor reaches a predetermined stepped position so as to direct an impulse to said second electromagnet. and operable further when said contactor has returned to its starting position to direct impulses to said first electromagnet, counting means for counting impulses directed to said second electromagnet, reset means for said counting means and second relay means operable when a predetermined number of impulses to said second electromagnet have been counted and said cortactor reaches another predetermined stepped position for causing an impulse to be directed to said second electromagnet and for causing the operation of said reset means.

ARCHIE J. MCMASTER. 

